SW76

Location: Tulloh

Australian Soil Classification: Vertic, Mottled-Subnatric, Brown SODOSOL

General Landscape Description: Undulating low hills.
Site Description: Waxing upper slope, 10%, eastern aspect.
Geology: Tertiary sediments (either Dilwyn or Eastern View Formation.

Soil Profile Morphology:

Surface Soil

A1	0-15 cm	Very dark gray (10YR3/1 moist), gray (10YR 5/1 dry); sandy loam; weakly pedal; pH 5.5:	SW76 Profile. Note: Surface (A1) horizon has been stripped from the soil profile.
A21ec	15-50 cm	grayish brown (10YR5/2 moist), conspicuously bleached (10YR7/1 dry); sandy loam; apedal, massive; minor small buckshot (breaking with moderate force); pH 5.6; abrupt change to:
A22	50-70/80 cm	Yellowish brown (10YR5/6 moist), brownish yellow (10YR6.5/6 dry); apedal; sporadic bleach; pH 5.9; clear change to:
Subsoil
B21tss	70/80-135 cm	Mottled strong brown (7.5YR5/8 moist), yellowish brown (10YR5/4 moist), brown cutans (10YR5/3 moist); heavy clay; vertic; very coarse blocky structure [80-100 mm]; some very large slickensides, up to 1 m across; pH 6.0; gradual change to:
B22tg	135 cm+	Dark gray (10YR4/1 moist) and white (10YR8/1 moist); heavy clay; red mottles (10R4/8 moist); polyhedral structure; slickensides (50-150 mm); pH 5.4.

• Deep, conspicuously bleached subsurface (A2) horizons.
• Strong texture contrast between surface (A) horizons and subsoil (B2) horizon.
• Vertic features (i.e. slickensides) in subsoil.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Low	Non-Sodic	None
Subsoil (B21 horizon)	Moderately Acid	Very Low	Marginally Sodic	*
Deeper Subsoil (at 110+ cm)	Strongly Acid	Very Low	-	*
* No results

The surface soil is strongly acid. The subsoil is moderately acid becoming strongly acid with depth.

Salinity rating is low in the surface becoming very low in the subsoil.

The soil is non sodic in the surface becoming marginally sodic in the subsoil.

The clay content increases markedly at the A/B boundary.

Horizon	Sample Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	NaCl %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
A1	0-15	5.5	4.8	0.11		2.9	1.2	0.41	0.2
A21ec	30-45	5.6	4.7	<0.05		1.2	0.87	<0.05	0.1
A22	55-70	5.9	4.9	<0.05		0.7	2.1	<0.05	0.32
B21tss	90-120	6	5	0.12		2.3	9	0.1	1.4
B21tg	150-170	5.4	4.5	0.14	0.02

Horizon	Sample Depth (cm)	Exchangeable Aluminium mg/kg	Organic Carbon %	Nitrogen %	Exchangeable Acidity meq/100g	Field Capacity pF2.5	Wilting Point pF4.2	Coarse Sand (0.2- 2.0 mm)	Fine Sand (0.02- 0.2 mm)	Silt (0.002- 0.02 mm)	Clay (<0.002 mm)
A1	0-15	49	5.3	0.39	17	30.1	11.1	14	38	19	17
A21ec	30-45	32			8.6	19.7	5.9	16	44	21	15
A22	55-70	<10			4	19.8	8.1	16	41	17	25
B21tss	90-120	28			10			5	10	6	74
B21tg	150-170

Management Considerations:

Subsoil (B) Horizons

• The subsoil displays vertic features (i.e. slickensides) which indicates that significant shrinking and swelling occurs during wetting and drying cycles. This may have engineering implications and is likely to explain the variability in surface horizon depth across the trench.

• Gleying in subsoil increases down slope from profile.